Resin-packaged protection circuit module for rechargeable batteries and method of making the same

ABSTRACT

A protection circuit module for rechargeable batteries includes a substrate, electronic components mounted on the obverse surface of the substrate for forming a protection circuit for rechargeable batteries, a housing mounted on the obverse surface of the substrate and including a top wall partially defining an enclosure for accommodating the electronic components, and a resin sealer loaded in the enclosure of the housing for sealing the electronic components. The top wall of the housing includes an opening for loading the resin sealer into the housing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a protection circuit module forrechargeable batteries and a method of making the same.

2. Description of Related Art

A protection circuit module for rechargeable batteries preventsover-discharge from and overcharge to rechargeable batteries and isconnected to the rechargeable batteries inside a battery pack for amobile phone for example.

FIGS. 6 and 7 a–7 c show a conventional protection circuit module forrechargeable batteries. As shown in the figures, the protection circuitmodule, generally indicated by a reference numeral 61, comprises asubstrate 62 in the form of a plate, a plurality of electroniccomponents 63 mounted on the obverse surface of the substrate 62, and aresin sealer 64 sealing the electronic components 63. The substrate 62is provided with a housing 65 enclosing the electronic components 63 andthe resin sealer 64, and a conductor plate 66 is attached to eachlongitudinal end of the substrate 62.

The housing 65 includes a top wall 65 a, a pair of lateral walls 65 bextending longitudinally of the substrate 62 from the top wall 65 a anda pair of end walls 65 c extending widthwise of the substrate 62 fromthe top wall 65 a. These walls define an enclosure for enclosing theresin sealer 64 and the electronic components 63. The resin sealer 64provides waterproof effect to prevent the electronic components 63 fromadversely affected by e.g. rain water coming into the battery pack ofthe mobile phone where the protection circuit module is incorporated.The resin sealer also protects the electronic components 63 fromexternal force or damage.

As shown in FIGS. 7 a–7 c, the housing 65 has an outer surface providedwith terminals 67 each including a contact portion 68 a plated withgold, and the substrate 62 has a reverse surface provided with terminals68 likewise plated with gold. These terminals 67, 68 are electricallyconnected to the electronic components 63, via a wiring pattern (notshown) formed on the obverse surface of the substrate 62, as well as amobile phone body (not shown) or an external battery charger (notshown). The inner ends of the conductor plates 66 are electricallyconnected to the electronic components 63 via the wiring pattern (notshown) within the housing 65, whereas the outer ends projecting out ofthe substrate 62 are electrically connected to the rechargeablebatteries (not shown) accommodated inside the battery pack (not shown).

The fabrication process of the protection circuit module 61 includessteps of mounting the electronic components 63 and the conductor plates66 onto the substrate 62, applying the resin sealer 64 over theelectronic components 63, and mounting the housing 65 onto the substrate62. Among these three steps, the step of mounting the electroniccomponents 63 and the conductor plates 66 as well as the step ofmounting the housing 65 are both performed by reflow soldering, wherebyif these two steps are performed at the same time, efficiency andproductivity will improve.

However, the step of mounting the housing 65 onto the substrate 62cannot be performed until the resin sealer 64 is applied over theelectronic components 63. Therefore, these three steps must be taken oneafter another as long as the conventional structure shown in FIGS. 6 and7 a–7 c is employed, whereby efficiency is difficult to improve.

Further, the resin sealer 64 is already applied when the housing 65 isbonded to the substrate 62 by reflow soldering, so that a heat-resistantthermosetting resin must be used for the resin sealer 64 to withstandhigh temperature of reflow soldering. A heat-resistant thermosettingresin, however, tends to contract when hardened, which may cause thesubstrate 62 to warp. Still further, a short circuit may occur betweenthe electronic components 63 when the housing 65 is mounted to thesubstrate 62 by reflow soldering, because solder which serves as a bondbetween the substrate 62 and the electronic components 63 re-melts andexpands. Still further, the screen printing method cannot be adopted forapplying a solder paste to the substrate 62 after the electroniccomponents 63 is mounted and the resin sealer 64 is applied, so thatsoldering for mounting the housing 65 must be performed manually, whichalso results in inefficiency

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide aprotection circuit module, wherein a plurality of electronic componentsand a housing can be mounted to a substrate at the same time.

It is another object of the present invention to provide a method ofmaking such a protection circuit module.

A protection circuit module provided in accordance with a first aspectof the present invention comprises: a substrate; electronic componentsmounted on an obverse surface of the substrate for forming a protectioncircuit for rechargeable batteries; a housing mounted on the obversesurface of the substrate and including a top wall partially defining anenclosure for accommodating the electronic components; and a resinsealer loaded in the enclosure of the housing for sealing the electroniccomponents. The top wall of the housing includes an opening for loadingthe resin sealer into the housing.

Functions and advantages of such a protection circuit module will bedescribed later in detailed description of preferred embodiments.

Preferably, the opening is formed in the middle of the top wall of thehousing.

Preferably, the resin sealer is hardenable at normal temperature, whichmay be silicone resin for example.

Preferably, the resin sealer is loaded into contact with the top wall ofthe housing. More preferably, the resin sealer has an exposed surfacesagging gently from edges of the opening of the housing.

Preferably, the housing includes a pair of lateral walls and a pair ofend walls defining the enclosure together with the top wall, the lateralwalls and the end walls abutting the substrate.

In a preferred embodiment of the present invention, the housing isrectangular and includes notched spaces at four corners beneath the topwall. The housing also includes a group of terminals, each extendingfrom the top wall to the substrate along relevant vertical wallspartially defining the notched spaces. A reverse surface of thesubstrate may be formed with another group of terminals conductive tothe electronic components. The obverse surface of the substrate may beformed with a plurality of conductor plates extending outwardly frominside the enclosure of the housing.

According to a second aspect of the present invention, a method isprovided for making a protection circuit module for rechargeablebatteries, the protection circuit module comprising: a substrate;electronic components mounted on an obverse surface of the substrate forforming a protection circuit for rechargeable batteries; a housingmounted on the obverse surface of the substrate and including a top wallpartially defining an enclosure for accommodating the electroniccomponents; and a resin sealer loaded in the enclosure of the housingfor sealing the electronic components; wherein the top wall of thehousing includes an opening for loading the resin sealer into thehousing. The method comprises a step of bonding the electroniccomponents and the housing onto the substrate simultaneously by heating,and a step of loading the resin sealer into the enclosure through theopening in the top wall of the housing.

Preferably, the step of simultaneously bonding the electronic componentsand the housing onto the substrate is performed by reflow soldering.

Preferably, the resin sealer is caused to harden at normal temperatureafter the step of loading. In that case, silicone resin may be employedfor the resin sealer.

Other features and advantages of the present invention will becomeapparent from the following detailed description of a preferredembodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view showing a protection circuitmodule in accordance with an embodiment of the present invention.

FIG. 2 a is a plan view showing the protection circuit module.

FIG. 2 b is a sectional view taken along lines IIb—IIb in FIG. 2 a.

FIG. 2 c is a bottom view showing the protection circuit module.

FIG. 3 a is a schematic perspective view showing a battery pack with theprotection circuit module incorporated inside.

FIG. 3 b is a perspective view showing the battery pack from a differentangle.

FIG. 4 is a sectional view taken along lines IV—IV in FIG. 2 b.

FIG. 5 is a perspective view illustrating a resin loading step in thefabrication process of the protection circuit module shown in FIG. 1.

FIG. 6 is a partially broken perspective view showing a conventionalprotection circuit module.

FIG. 7 a is a plan view showing the conventional protection circuitmodule.

FIG. 7 b is a longitudinal sectional view showing the conventionalprotection circuit module.

FIG. 7 c is a bottom view showing the conventional protection circuitmodule.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, a detailed description is given on a preferred embodiment of thepresent invention with reference to the accompanying drawings.

FIGS. 1 and 2 a–2 c show a protection circuit module 1 in accordancewith the preferred embodiment of the present invention. FIGS. 3 a and 3b show the same protection circuit module 1 incorporated in a batterypack 10 for a waterproof mobile phone for example. The protectioncircuit module 1, when incorporated in the battery pack 10, is connectedto a plurality of rechargeable batteries (not shown) also accommodatedinside the battery pack 10 for prevention of over-discharge from andovercharge to the batteries.

As shown in FIG. 1, the protection circuit module 1 comprises asubstrate 2 in the form of a rectangular plate made of e.g.glass-fiber-reinforced epoxy resin, electronic components 3 mounted onthe obverse surface of the substrate 2, and a housing 4 mounted on theobverse surface of the substrate 2 enclosing the electronic components3. The housing 4 defines an enclosure filled with a resin sealer 5.

The obverse surface of the substrate 2 is provided with a wiring pattern(not shown) formed by etching a copper foil for example. This wiringpattern includes a plurality of conductor pads (not shown), and iselectrically connected to the electronic components 3. The electroniccomponents 3 are outwardly connected via these conductor pads as will bedescribed below.

The housing 4 includes a top wall 4 a corresponding in shape to thesubstrate 2, a pair of lateral walls 4 b extending longitudinally of thesubstrate 2, and a pair of end walls 4 c extending widthwise of thesubstrate 2. Conductor plates 6 are inserted into the housing 4 throughthe end walls 4 c. The resin sealer 5 may be made of silicone resin forexample, whereas the conductor plates 6 may be made of nickel forexample.

The top wall 4 a of the housing 4 is formed with an opening 7 at themiddle thereof. As described hereinafter, the resin sealer 5 is loadedinto the housing 4 through this opening 7. The lateral walls 4 b and theend walls 4 c, defining the periphery of the housing 4, are notched atfour corners of the housing 4. In other words, each of the cornersbeneath the top wall 4 a is formed with a notched space which ispartially defined by a first vertical wall 4 d extending widthwise ofthe substrate 2, and a second vertical wall 4 e extending longitudinallyof the substrate 2. The technical significance of the notched space willbe explained later.

As shown in FIGS. 1, 2 a, and 2 b, the housing 4 is formed with a firstgroup of terminals 8. The respective terminals 8 are bent copper plateswhich are attached to the housing 4 by being inserted when the housing 4is molded with resin. On the top wall 4 a of the housing 4, therespective terminals 8 include a contact portion 8 a plated with goldfor example. When the protection circuit module 1 is enclosed in thebattery pack 10 as shown in FIG. 3 b, the contact portions 8 a areexposed to the outside through upper openings 10 a of the battery pack10 for electrical connection to the mobile phone body (not shown).

As shown in FIG. 4, each of the terminals 8 has leg portions 8 bextending from the top wall 4 a of the housing 4 down to the obversesurface of the substrate 2. As previously described, each of the fourcorners of the housing 4 is formed with a notched space. Each legportion 8 b of the terminal 8 is exposed to the outside along thevertical wall 4 e which partially defines the notched space (see FIG.1). Therefore, the notched space may be utilized for effectivelysoldering the leg portion 8 b of the terminal 8 and a respectiveconductor pad (not shown) of the wiring pattern (not shown) on thesubstrate 2. The notched space also facilitates visual check of thesoldering.

As indicated in FIGS. 2 b and 2 c, the reverse surface of the substrate2 is formed with a second group of terminals 9. Each of the terminals 9includes an outer surface plated with gold for enhancing contactconduction. When the protection circuit module 1 is incorporated in thebattery pack 10 as shown in FIG. 3 a, the terminals 9 are exposed to theoutside through lower openings 10 b of the battery pack 10 forelectrical connection to an external charger (not shown) The terminals 9are also electrically connected to the relevant conductor pads (notshown) via through-holes, lined with conductive elements, penetratingthicknesswise of the substrate 2.

One of the two conductor plates 6 operates as an anode whereas the otheroperates as a cathode. Within the housing 4, the inner ends of therespective conductor plates 6 are electrically connected to theelectronic components 3 via the wiring pattern on the substrate 2. Onthe other hand, the outer ends of the respective conductor plates 6projecting out of the substrate 2 are electrically connected to therechargeable batteries (not shown) within the battery pack 10.

The protection circuit module 1 of the above-described structure may befabricated in the following manner.

First, solder paste is applied by the printing method to portions of asubstrate 2 where electronic components 3, a housing 4 and conductorplates 6 are to be mounted. In particular, the solder paste is appliedto the relevant conductor pads (not shown) of the wiring pattern (notshown) on the substrate 2.

Then, the electronic components 3, the housing 4 and the conductorplates 6 are automatically mounted on the substrate 2 by using a holdingdevice (not shown) such as a suction collect. At this time, theelectronic components 3, the housing 4 and the conductor plates 6 areappropriately positioned relative to the relevant conductor pads (notshown) of the wiring pattern (not shown) on the substrate 2.

Then, the solder paste is heated for melting in a reflow oven, followedby cooling for solidification. In this way, the electronic components 3,the housing 4, and the conductor plates 6 are all mounted onto thesubstrate 2 at a time by reflow soldering.

Finally, as shown in FIG. 5, the housing 4 is filled with a resin sealer5 by using an injection nozzle 10 inserted into the housing 4 throughthe opening 7 formed in the top wall 4 a, for sealing all the electroniccomponents 3. The extent of the resin filling is such that the resindoes not leak through clearances between the housing 4 and the substrate2, nor does it overflow onto the top wall 4 a of the housing 4 above theopening 7. Specifically, as shown in FIG. 2 b, the resin filling isperformed until an exposed surface of the resin sealer 5 at the opening7 sags gently from the edges of the opening 7.

The protection circuit module 1 is thus completed by the above-describedmethod. In this method, since the opening 7 is formed in the top wall 4a of the housing 4, the housing 4 can be mounted to the substrate 2before the resin sealer 5 is loaded for waterproof treatment of theelectronic components 3. Therefore, the electronic components 3, thehousing 4, and the conductor plates 6 are all mounted to the substrate 2at the same time by reflow soldering. As a result, the efficiency of thefabrication process improves by automating the series of process stepswhich include applying the solder paste onto the substrate 2, mountingthe electronic components 3, the housing 4 and the conductor plates 6onto the substrate 2 by reflow soldering, and waterproofing theelectronic components 3 (filling the resin sealer 5). The filling of theresin sealer 5 can be performed after the reflow soldering treatmentwhich requires heating, whereby there is no need to consider heatresistance and silicone resin hardenable at normal temperature withoutcontraction may be employed as the resin sealer 5.

In the embodiment shown in the figures, since the opening 7 formed inthe middle of the top wall 4 a of the housing 4 is relatively large,heat inside the reflow oven can be efficiently led into the housing 4,and the housing 4 can be filled almost uniformly with the resin sealer5. Further, the lateral walls 4 b and the end walls 4 c abut on thesubstrate 2 to restrain leakage of the resin sealer 5 filled in thehousing, thereby reducing the disadvantages that would otherwise arisefrom resin leakage.

The preferred embodiment of the present invention being thus described,the present invention is not limited to that embodiment. For example,shapes of the housing 4 and the opening 7 are not limited to those shownin the figures, and shapes, sizes, and positions of the conductor plates6 and the terminals 8, 9 are not limited to those in the figures. Thesolder paste is not necessarily applied in advance to the substrate 2,but can be applied in advance to the electronic components 3 mounted onthe substrate 2. Therefore, the present invention can be varied invarious ways unless the variations depart from the spirit and the scopeof the claims given below.

1. A protection circuit module for rechargeable batteries comprising: asubstrate; electronic components mounted on an obverse surface of thesubstrate for forming a protection circuit for rechargeable batteries; ahousing mounted on the obverse surface of the substrate and including atop wall partially defining an enclosure for accommodating theelectronic components; a plurality of terminals provided on the housing;and a resin sealer loaded in the enclosure of the housing for sealingthe electronic components; wherein the top wall of the housing includesan opening for loading the resin sealer into the housing; wherein thehousing is rectangular and includes notched spaces at four corners ofthe housing beneath the top wall, the plurality of terminals beingexposed at the notched spaces at least partially.
 2. The protectioncircuit module for rechargeable batteries according to claim 1, whereinthe opening is formed in the middle of the top wall of the housing. 3.The protection circuit module for rechargeable batteries according toclaim 1, wherein the resin sealer is hardenable at normal temperature.4. The protection circuit module for rechargeable batteries according toclaim 3, wherein the resin sealer is silicone resin.
 5. The protectioncircuit module for rechargeable batteries according to claim 1, whereinthe resin sealer is loaded into contact with the top wall of thehousing.
 6. The protection circuit module for rechargeable batteriesaccording to claim 5, wherein the resin sealer has an exposed surfacesagging gently from edges of the opening of the housing.
 7. Theprotection circuit module for rechargeable batteries according to claim1, wherein the housing includes a pair of lateral walls and a pair ofend walls defining the enclosure together with the top wall, the lateralwalls and the end walls abutting the substrate.
 8. The protectioncircuit module for rechargeable batteries according to claim 1, whereineach of the terminals extends from the top wall to the substrate alongrelevant vertical walls partially defining the notched spaces.
 9. Theprotection circuit module for rechargeable batteries according to claim1, wherein a reverse surface of the substrate is formed with anothergroup of terminals conductive to the electronic components.
 10. Theprotection circuit module for rechargeable batteries according to claim1, wherein the obverse surface of the substrate is formed with aplurality of conductor plates extending outwardly from inside theenclosure of the housing.